Pseudo Static Test And Numerical Study Of Precast Segmental Bridge Columns With UHPFRC Bottom Segment

Precast segmental bridge columns have the advantages of low environmental impact,short construction period,good construction safety and easy construction quality assurance,which have paied more attention focus in the field of bridge engineering at home and abroad.By summarizing and analyzing the seismic performance analysis of precast segmental bridge columns so far,it is found that the main structural damage are concentrated at the bottom segment and the connection types.In view of these,this paper proposed and designed four precast segmental bridge columns considering the application of new materials and component forms of the bottom segment,in order to improve the seismic performance of such bridge columns.This paper summarizes and introduces the research progress of precast segmental bridge columns from the aspects of connection types of prefabricated components,adding energy dissipation devices,combination of various components and application of new structural materials.In order to improve the bearing capacity and energy dissipation capacity of traditional precast segmental bridge columns,Ultra High Performance Fiber Reinforcing Concrete(UHPFRC)could be used to replace the ordinary concrete in the bottom segment,as the key stress region.Then,the three-dimensional solid element models are established according to the quasi-static test specimens,and some design parameters are used to analyze the influence on seismic performance of precast segmental bridge columns based on the numerical models.The main research work is as follows:(1)Four precast segmental bridge columns specimens are designed and constructed,considering three main aspects at bottom segment: concrete material,hollow or solid,combination of component.Then,qasi-static tests are carried out to discuss the damage pattern,hysteretic performance,energy dissipation capacity and joint opening of precast segmental bridge columns with UHPFRC at bottom segment.(2)According to the four experimental specimens with same parameter and loading pattern,the three-dimensional solid element models are established by ABAQUS,and the numerical results are compared with the experimental results to verify the usefulness of the modeling method.(3)Based on the established numerical models,parameter study of precast segmental bridge columns are carried out.The three parameters,icluding initial prestress level,hollow ratio of bottom segment,the height ratio of bottom segment are selected to establish the corresponding numerical models.Then,the influence of design parameters on seismic performance of the precast segmental bridge columns is studied through the numerical results.The main conclusions are as follows:(1)The use of UHPFRC at the bottom segment could obvious reduce the damage of structural concrete and increase the lateral bearing capacity and energy dissipation capacity to a certain extent.Under the premise of guaranteeing the shear resistance,hollow or solid UHPFRC section at the bottom all could increase the bearing capacity and energy dissipation capacity of precast segmental bridge columns to a certain extent and hollow UHPFRC section is considered to be more cost-effective in engineering.The combination of the outer hollow UHPFRC and the common concrete inner column at the bottom could effectively improve the seismic performance of the columns,and and at the same time transfer the damage to the foot of the upper column to ensure the structural damage of the key parts.(2)Considering the concrete damage,lateral force and cumulative energy dissipation,the results of numerical model calculation are compared with the experimental results.It is found that the two models have similar changing rules and are in good agreement.The availability of the numerical simulation method and models is verified.(3)Increasing the initial prestressing level can greatly improve the load bearing capacity and energy dissipation capacity of precast segmental bridge columns with UHPFRC at the bottom.On the premise of ensuring structural stability,the change of the hollow ratio of UHPFRC at the bottom has little influence on the seismic performance of piers.In this paper,piers with hollow ratio of 0.5 at the bottom have relatively large lateral load and energy dissipation capacity and could control the structural damage degree.The increase of height ratio of bottom segment could make the columns gradually form the plastic hinge area at the bottom segments,similar to the monolithic cast-in-place bridge piers.The inner ordinary concrete column would bear larger plastic deformation,which could effectively improve the bearing capacity and energy dissipation of the columns.